Process of making betulin suitable for the production of coating compositions thereof.



UNITED STATES PATENT-OFFICE.-

J'OEAN ROBERT KOHLER; OF STOCKHOIM, SWEDEN.

success or Maxine Bn'rnmn surname son THE raonuor'ron or comma COMPOSITIONS THEREOF.

1,016,162; No Drawing.

Patented Jan. 30,1912.

To all whom it may concern Be it known that I, .JOHAN ROBERT -K6HLER, a citizen of the Kingdom of Sweden, residing at Stockholm, Sweden, have invented a new and useful Im roved Process of Making Betulin Suitable or the Production of Coating Compositions There- 01'', of which the following is a specification.

In the manufacture of coating compositions of betulin as a substitute for usual lacvarnishes and the like certain difiiculties arise which are due partly to the small solubility of the betulin in cold solvents, partly to the tendenc of the betulin to crystallize when the solvent is removed.

Pure betulin produced in the usual manner is dissolved only in little degree in cold solvents such as alcohol, while the solubility is increased essentially in heated solvents, but when the latter are cooled the excess of the dissolved betulin again crystallizes, and on account thereof it is not possible in this wayto produce coating compositions containing'betulin as an ingredient.

If the betulin be molten it becomes again crystalline when growing solid by cooling. The melting 'oint of such'betu'lin as well as the solubility conditions are the same as those of betulin which has not been molten. First by heating the betulin considerably above'its melting point during a sufficiently longtime it is possible to increase its solubility in such a degree that it can .be'used for the present purpose. Betulin treated in such a manner does not crystallize from a concentrated heated solution thereof when the latter is cooled, and the solution has properties which make it quite ea pial to a good lac-varnish, inasmuch as the betulin when the solvent is dried or removed becomes solid and forms a mass of glassy structure. The heatin of the betulin that is used according to t e present invention is va'ried' according as the betulin is heated alone or in a solution and also according. to the length of the time of heating. Ifthe betulin is heated alone, the temperature must be increased considerably above the melting point (about 50-120 C. above the melting point), and, inasmuch as \the:-betu-lin rap idly assumes a dark color when heated to such a hi h temperature in air on account of:

partial ecomposition, the heating should suitably be made either in vacuum or in an indifferent gas atmosphere. The time of heat-mg may be varied from one to twent hours depending on the temperature use a higher temperature rendering it possible w1th 1n certain limits to use a shorter time of heating. Any exact limits for temperature and time of heating may, however, not be given, inasmuch as such limits depend on the quantity treated, the degree of purity of thebetulin, the stirring of the molten mass,

the pressure used and so on. Generall the temperature and the time of heatingi't ere fore must be determined empirically in each special case; The purpose ofthe heating is reached when. the mass is rather easily dissolved in hot turpentine 'oil and when from a concentrated solution thereof no precipitation takes place when the solution is cooled. The melting point of the mass is generally about 130-140 C. and of the same may be produced cold solutions containin up to' 50% of betulin or more, while usua crystallized or only molten betulin is dissolved hardly to one percentage in cold solvents.

How the betulin during the heating according to the present invention is changed cannot yet be decided. Probably an inner reconstruction of the betulin molecule takes place as is the case with the natural resin acids, the sapin acids, which when heated are transformed into isomeric colophon acids having quite other properties than the original acids as to their relation to polarized light, their solubility, melting point and -so on. The melting point generally sinks the more the higher temperature is that is used and the longer the time is during which the betulin is heated. If the heating is made duringa too long time or at a too high temperature the betulin can be transformed into a half solid, sticky, non-drying mass.

Experiment 1: Betulin was heated in a vacuum of 20 to 30 mm. mercury pressure with and without admitting a current of an indifierent' gas, for instance carbonic acid (G0,),fo1 the purpose stirring. Good gave thesame result. The melting point of the finQLEI-Qdlltit was about 140 C. Good lac-varngis same whilgiusing well lm'own solvents, such as linseed oil, turpentine oil, acetone and so on,

Experiment 2: Betulin was heated at usual pressure in an atmosphere of (30,.

Good results were reached by using a temperature of 350 to 370 C. and a heating during about four hours. The product obtained was similar to that described under Experiment 1 but was of a somewhat darker color.

Experiment 3: Betulin was heated under pressure in an atmosphere of CO A soluble product with a melting point of 130 to 135 C. was obtained by usmg a temperature of 360 to 370 C. and a time of heating of about three hours. At higher temperature (for instance 400 C.) decomposition took place and the product became darkbrown. Also, a too long-time of heating proved itself to be unfavorable. Thus the betulin heated during five hours to 365 C. was transformed into a yellow-brown, halfsolid, non-drying mass. Heating to a lower temperature than 360 C. during a longer time resulted in an amorphous glassy mass, which was diflicult to dissolve and therefore could ndt be used for the present purpose. Thus at a temperature of 340 C. and a time of heating of fifteen hours an unsoluble product was obtained. The latter had a melting point of 232 C.

Instead of heating the betulin alone, as described above, one may accomplish the transformation thereof by taking it up successively into a hot solvent, for instance linseed oil. or turpentine oil, or a mixture of these oils under pressure.

Betulin in its natural state is diflicult to dissolve in linseed or turpentine oil on account whereof it precipitates in a crystalline or amorphous state from hot solutions of usual betulin in linseed or turpentine oil when the solutions are cooled. If however the beta-hippie dissolved in the solvent by heatingtlcsiilatter under pressure to temperatures above the melting point of the betulin, a lac will be obtained which may contain 50% of betulin or more, and the betulin does not precipitate from the solution when the latter is cooled. Clear solutions of crystallized betulin in linseed oil (or turpentine oil) have been obtained at a temperature of 255280 C. and a time va ing between 30 minutes and 5 hours. Kt the shorter time solutions containing about es could be manufactured of the orena 26% of betulin were obtained, t; at th longer time thesolutions contained about 50% of betulin. Betulin extracted from the last mentioned solutions had a melting point of about 190-l95 CL- For making betulin suitable as an ingredient of coating compositions one may use both of the above described methods in the following manner. The betulin is first molten and heated alone above its melting point but at a lower temperature or at a shorter time than is required forcomplete transformation of the same, whereupon the product thus obtained is dissolved in a suitable solvent which is heated to such a high temperature and during such a period of time that a complete transformation of the betulin takes place. Said combined method is preferred when the invention is to. be

carried into practice on large scale, inas-' much as it is possible to; use comparatively low temperatures and the product obtained thus becomes more colorless than otherwise. Also in this case temperature and timerof heating must be determined empirically.

Having now described my invention what I claim is:

1. The rocess described of making betulin suitab e for the production 'of coating point, through such process described of making betue for the production of coating.

ing the betulin in an indifferent, gas atmosphere to a temperature considerably above its melting point through such a periodof time that it, does not precipitate from a hot concentrated solution thereof when the latter is cooled, and that it, when the solvent becomes dry or is removed, grows solid and forms a body of a hard, glassy or lac-like structure.

3. The process described of making betulin suitable for the production of coating compositions thereof which consists in heating the betulin in an indifferent gas atmosphere and at a higher pressure than that of the atmosphere to a temperature considerably above its melting point such a period of time that it does not precipitate from a hot concentrated solution thereof when the latter is cooled, and that it, when the solvent becomes dry or is removed, grows solid and forms a body of a hard, glassy orlaclike structure.

4. The process described of making betulin suitable for the profiuction of coating moved, grows solidand forms a body of a 10 I composition thereof which consists in heathard, glassy or-lac-like structure. ing the betulin alone to a temperature con- In' testimony that I claim the foregolng siderably above its melting point and then as my mv'entlon, I have signed my name 1n heating it together within a suitable solvent presence of two subscribmg wlt'nesses.

at such 'a temperature through such afperiod JOHAN ROBERT KQHLER.v of time that it does notprecipitate om' a Witnesses: V I hotconcentrated solution thereof and that LUND DELMAY,

it, when the solvent becomes dry or is re- TORVALD Nvs'rnom. 

